How to move forward

How to move forward

I am trying to trace the children of my grandfathers 1st marriage (my aunts). My father was by my grandads second marriage.

I posted previously asking where to begin I know - my grandads full name ( knew that anyway) -the name of his 1st wife including her maiden name. - there marriage date this is still a question mark at the minute but I can find the 2 names getting married in the right area in 1940, so for now at least this is when I think they married My grandad remarried in 1945 so I know the children(2 girls I believe) must have be born between 1940 and 1945.

Anyone have any suggestions as to how the heck I go about finding them from here?